There are many aqueous industrial systems which require that various materials remain in a soluble, or suspended, or dispersed state. Typical aqueous systems include, for example, boiler water or steam generating systems, cooling water systems, gas scrubbing systems, pulp and paper mill systems, desalination systems, and downhole systems encountered during the production of gas, oil, and geothermal wells. In many cases, water contains (either naturally or by contamination) ingredients, such as inorganic salts, which can cause accumulation, deposition, and fouling problems. These salts are formed by the reaction of metal cations, such as calcium, magnesium or barium, with inorganic anions such as phosphate, carbonate and sulfate. These salts have low solubilities in water and as their concentration in solution increases, or as the pH or temperature of the water containing them increases, these salts tend to precipitate from solution, crystallize and form hard deposits or scale on surfaces. Scale formation is a problem in heat transfer devices, boilers, secondary oil recovery wells, automatic dish washers and on substrates washed with such hard waters.
Many cooling water systems, including industrial cooling towers and heat exchangers, made from carbon steel experience corrosion problems. Corrosion is combated by the addition of various inhibitors such as orthophosphate compounds and/or zinc compounds. The addition of phosphates, however, adds to the formation of highly insoluble phosphate salts such as calcium phosphate. The addition of zinc compounds can also lead to the precipitation of insoluble salts such as zinc hydroxide, and zinc phosphate. Other inorganic particulates, such as mud, silt and clay, are commonly found in cooling water. These particulates tend to settle onto surfaces and thereby restrict water flow and heat transfer unless they are effectively dispersed.
The stabilization of aqueous systems containing scale forming salts and inorganic particulates involves one or a combination of mechanisms. Dispersion of the precipitated salt crystals is another stabilization mechanism believed to be the result of the adsorption of the inhibitor onto precipitated crystals. The adsorption of the inhibitor can also be used to stabilize the system by facilitating the dispersion and subsequent removal of other suspended particulates, such as mud, silt and clay, and metals such as iron and zinc and their insoluble salts, from aqueous systems. Another stabilization mechanism involves the ability of the inhibitor to interfere with and distort the crystal structure of the scale making the scale less adherent to surfaces or other forming crystals or existing particulates.
Many different synthetic water soluble polymers have been employed in a wide range of water treatment applications as dispersants for particulate matter and inhibitors of mineral scale formation and deposition. Polymers containing carboxylic acid and/or sulfonic acid functionality have been found to be particularly useful.
U.S. Pat. No. 4,892,898 (issued Jan. 9, 1990 to J. Leighton, et al.) discloses water soluble polymers of allyloxybenzenesulfonate monomers and one or more copolymerizable monomers. U.S. Pat. No. 4,709,091 (issued Nov. 24, 1987 to Y. Fukumoto, et al.) discloses polymers of maleic acid and sodium methallyl sulfonate which may be used as a dispersing agent and a scaling inhibitor. U.S. Pat. No. 4,711,725 (issued Dec. 8, 1987 to D. Amick, et al.) discloses processes for stabilizing aqueous systems containing scale forming salts and inorganic particulates by adding to such systems low molecular weight water soluble polymers which contain (meth)acrylic acid units, acrylamido alkyl or aryl sulfonate units and one or more units selected from vinyl esters, vinyl acetate and substituted acrylamides. U.S. Pat. No. 4,504,643 (issued Mar. 12, 1985 to J. Boutin, et al.) discloses a water soluble (meth)acrylic acid/methallylsulfonate copolymer and a scale inhibitor for aqueous environments. U.S. Pat. No. 4,451,628 (issued May 29, 1984 to L. Dammann) discloses low molecular weight water soluble polymers made by copolymerizing methallyl sulfonic acid, or the alkali metal salts thereof, with water soluble monomers, which polymers may be used as dispersants or scale inhibitors. Even though there are numerous water treatment polymers, as indicated above, the water treatment industry is constantly looking for new processes and products which will provide more efficient operation of aqueous systems by maintaining water contaminants in a dispersed, suspended or soluble state under a wide range of process conditions.
Water soluble polymers are also of importance in other systems including, for example, high solid slurries, i.e. 25 to 85% solids, such as drilling muds, cementiferious compositions, pigment dispersions, mineral slurries and in detergent compositions.
In aqueous drilling muds, a dispersant's ability to deflocculate and disperse flocculated and agglomerated solids, especially in electrolyte-rich fluids, is highly desired. Conventionally used polyacrylates are known to be sensitive to divalent cations which may be introduced into a drilling fluid through electrolyte-releasing formations containing gypsum, lime and other salt deposits or by the water available to formulate the mud (e.g., sea water). There is still a need for new products which can provide rheological stability to polyelectrolyte containing drilling muds, and in particular to high solids muds (having densities greater than 15 pounds per gallon).
In cementiferious compositions, polymeric additives which improve the physical characteristics such as the flow and workability thereof are employed. The additives (often referred to as plasticizers) improve the flow characteristics of the compositions containing them so that they may be pumped or effectively poured to fill all the spaces in a mold or other structure. Such additives can be used to design cementiferous compositions with a reduced water content which still retains adequate flow properties.
In detergent compositions, polymers may impart many useful functions. They can function, either independently or concurrently, as viscosity reducers in the processing of powdered detergents, as antiredeposition agents, as scale and deposit inhibitors, as crystal modifiers, and as detergent assistants which are capable of completely or partially replacing the materials used as builders, while imparting to surfactants optimum properties with respect to detergent actions. Recent trends in the art have been to reduce or eliminate the use of inorganic phosphates due to environmental pollution problems. A variety of other methods of water softening have been employed, of which one of the most economical is the addition of alkali metal carbonate salts. However, these salts are effective by removing hardness ions via precipitation, thereby leaving unacceptable levels of residue on the washed articles. Polymers which exhibit both superior threshold inhibition, i.e., they can maintain the hardness ions in solution past their normal precipitation concentration, and crystal modification, which can prevent the unacceptable levels of residue adhering on the washed articles, are particularly preferred.
Polymers have found wide utility in machine dishwashing applications by performing many of the same functions as in fabric laundering formulations. However, polymers may be required to perform other functions due to differences in the formulations, the substrate being cleaned, and the machine itself. Machine dishwashing formulations vary from those for fabric laundering in that the dishwashing formulation contain cleaning agents that must be low foaming and, preferably, contain foam suppressors. As such, anionic surfactants, which aid in anti-redeposition in fabric laundering, are not used to a large extent in the automatic dishwashing detergents. Polymers are added which exhibit the ability to disperse particulate matter and thus prevent soils which have been removed from the article from agglomerating and re-adhering to the surface of the cleaned article. Machine dishwasher formulations differ from home laundry compositions in that most dishwashers require higher wash temperatures. Dishwashing machines typically utilize internal heating elements to increase the temperature of the tap water to the optimum. Under these conditions, the heating element often forms surface deposits which significantly reduce its efficiency. Polymers which can be used to remove these deposits are thus often added to machine dish formulation. In addition, the polymers must be hydrothermally stable at the higher wash temperatures.
Allyloxybenzenesulfonates have been copolymerized with acrylonitrile. The fibers produced from such copolymers have been found to have good basic and cationic dye receptivity. Methods for preparing the allyloxybenzenesulfonate monomers, the copolymerization of the monomers with acrylonitrile alone and with other olefinic monomers, and the fibers thereof are described in detail in the following references: Chemical Abstracts Volume 78 (1973), 78:84025h; U.S. Pat. No. 3,410,835 (issued Nov. 21, 1968 to C. Mazzolini, et al.); U.S. Pat. No. 3,426,104 (issued Feb. 4, 1969 to J. Masson); U.S. Pat. No. 4,163,089 (issued Jul. 31, 1979 to G. Palethorpe); U.S. Pat. No. 4,265,970 (issued May 5, 1981 to H. Bach); and U.S. Pat. Nos. 4,293,613 and 4,294,884 (issued October 6 and Oct. 13, 1981 respectively, to H. Bach, et al.).
While allyloxybenzenesulfonate monomer and the alkali metal salts of methallyl sulfonic acid have each been used independently in the treatment of water which contains inorganic particulate matter, none of the above references disclose or suggest the compositions of the present invention or their use in aqueous systems containing inorganic particulate matter. In particularly preferred embodiments of the present invention, synergistic properties are realized by combining an allyloxybenzenesulfonic acid monomer, a methallyl sulfonic acid monomer, a copolymerizable unsaturated carboxylic acid monomer and an alkyl ester monomer, in certain molar ratios. The novel compositions allow the replacement of a major portion of the relatively expensive allyloxybenzenesulfonic acid monomer with the relatively less expensive methallyl sulfonic acid monomer, without loss of the polymer's ability to inhibit the formation and deposition of inorganic mineral scale in an aqueous system and to disperse inorganic particulate matter in aqueous systems. In addition, the polymers of the present invention unexpectedly have been found to resolubilize and to stabilize pre-existing mineral scale deposits in such aqueous systems.